How to retrieve dupli data in 2.8?
From batFINGERS' answer:


  Instances can be obtained from the depsgraph.
  https://docs.blender.org/api/master/bpy.types.DepsgraphObjectInstance.html#module-bpy.types
  
  There is a section in
  
  https://wiki.blender.org/wiki/Reference/Release_Notes/2.80/Python_API/Scene_and_Object_API


So, bpy.context.evaluated_depsgraph_get().object_instances is a replacement for bpy.context.object.dupli_list